The present invention relates to rotary compressors and, more particularly, to such compressors with an improved discharge valve assembly of the span type.
Typically, rotary compressors include a hermetic outer casing in which there is disposed a refrigerant or other gas compressor unit. The compressor unit includes a cylindrical side wall and a pair of end plates defining a a cylindrical compression chamber. A roller is positioned in the chamber and is driven by an eccentric formed on a motor driven drive shaft. A vane is mounted in the cylindrical wall and rides against the roller to divide the chamber into a low pressure and a high pressure side. A discharge passage extends through one end plate to connect the high pressure side to the interior of the casing outside the compressor unit. The outer surface of the end plate is provided with a valve seat which surrounds the end of the discharge passage. A flapper valve mechanism is mounted to one side of and extends over the seat. The valve mechanism opens when the pressure of the refrigerant reaches a predetermined high level and allows high pressure gas to exit the chamber to the space inside the casing. The valve opens and recloses very quickly, for example, in no more than about 4/1000 of a second. In addition, it is desirable for the valve action to be clean and without flutter. Flapper valves tend to open from the side opposite their mounting and to close in the opposite manner, rather than to open and close perpendicularly to the seat. Moreover, flapper valves tend to have a reed action in that they vibrate from side-to-side and end-to-end and twist about their longitudinal axis. All of these characteristics detract from optimum operation of the valve assembly.